RFR: JDK-8146403: Windows build can be faster

[Erik Joelsson]

Hello,

During the hotspot makefile conversion, we have been reminded of 
inefficiencies when running make in Cygwin. We still have a pretty 
severe performance regression in the new hotspot build compared to the 
old on Windows in certain situations, my laptop being one such 
situation. A recent comparison there between just the old and new 
hotspot build:

release new 00:04:30
release old 00:03:10
fastdebug new 00:04:59
fastdebug old 00:03:37

Much of the extra time is spent spawning various shell processes for 
book keeping, like saving failure logs, creating header dependency files 
etc.

It also takes a very long time to do a "do nothing" rebuild when nothing 
has changed. On my laptop, repeating "make jimages" often takes as long 
as 40 seconds to figure out that nothing needs to be rebuilt. In this 
case there are several culprits.

I have been working on improvements in these areas to reduce the 
overhead. The "do nothing" rebuild of jimages is down to around 25 
seconds. A full images build is around 1-2 minutes faster from 24 to 22 
minutes, but fluctuates quite a bit. The new hotspot build is also 
improved:

release: 3:44
fastdebug: 4:02

Here is a list of the kinds of changes I've made:

* Rewrote logger.sh to use a different construct. It drastically reduces 
the number of bash processes being spawned. Basically you can pipe like 
this: "> >(tee logfile) 2> >(tee logfile >&2)". I also managed to reduce 
the extra sed/grep commands needed for the header dependencies even 
more. A side effect of this is that the log files for each native 
compilation unit are always saved instead of being deleted on successful 
compilation. I see no issue with this.

* Changed all recipes that contain echo for logging to instead use new 
LogInfo macro, which in turn calls $(info ) if appropriate.

* Changed all recipes that contain mkdir to instead use MakeDir macro, 
which only executes mkdir if the directory doesn't exist.

* In HotspotWrapper.gmk there is an optimization to avoid calling the 
hotspot makefiles at all if nothing has changed. This runs a find over 
the whole hotspot repository. I reduced this to only run over src and 
make sub dirs to avoid the pretty large test dir (since test/closed has 
grown quite a bit).

* Split Tools.gmk into CompileTools.gmk and Tools.gmk, to avoid having 
the buildtools compilation being reevaluated by all makefiles needing 
the tools definitions.

* Split Modules.gmk to avoid having the module deps generation being 
reevaluated multiple times. Made the new GenerateModuleDeps.gmk an 
explicit call from Init.gmk.

Since these improvements affect much more than just the new hotspot 
build, I intend to push this to JDK 9 directly.

Bug: https://bugs.openjdk.java.net/browse/JDK-8146403
Webrev: http://cr.openjdk.java.net/~erikj/8146403/webrev.01/

/Erik